--- a/dom/xul/XULDocument.cpp
+++ b/dom/xul/XULDocument.cpp
@@ -1161,19 +1161,21 @@ XULDocument::Persist(Element* aElement, 
     if (NS_WARN_IF(NS_FAILED(rv))) {
         return rv;
     }
 
     if (hasAttr && valuestr.IsEmpty()) {
         return mLocalStore->RemoveValue(uri, id, attrstr);
     }
 
-    // Persisting attributes to windows is handled by nsXULWindow.
+    // Persisting attributes to top level windows is handled by nsXULWindow.
     if (aElement->IsXULElement(nsGkAtoms::window)) {
-        return NS_OK;
+        if (nsCOMPtr<nsIXULWindow> win = GetXULWindowIfToplevelChrome()) {
+           return NS_OK;
+        }
     }
 
     return mLocalStore->SetValue(uri, id, attrstr, valuestr);
 }
 
 
 nsresult
 XULDocument::GetViewportSize(int32_t* aWidth,
@@ -1753,19 +1755,22 @@ XULDocument::ApplyPersistentAttributesTo
 
         uint32_t cnt = aElements.Count();
         for (int32_t i = int32_t(cnt) - 1; i >= 0; --i) {
             RefPtr<Element> element = aElements.SafeObjectAt(i);
             if (!element) {
                  continue;
             }
 
-            // Applying persistent attributes to windows is handled by nsXULWindow.
+            // Applying persistent attributes to top level windows is handled
+            // by nsXULWindow.
             if (element->IsXULElement(nsGkAtoms::window)) {
-                continue;
+                if (nsCOMPtr<nsIXULWindow> win = GetXULWindowIfToplevelChrome()) {
+                    continue;
+                }
             }
 
             Unused << element->SetAttr(kNameSpaceID_None, attr, value, true);
         }
     }
 
     return NS_OK;
 }